More precise detection of old pages. [launch codename "oldn23", project codename “Freshness"] This change improves detection of stale pages in our index by relying on more relevant signals. As a result, fewer stale pages are shown to users.
This seems to be the most significant point of the 50 updates in March. I can see websites with fast changing content doing really well now.
One in particular has overtaken every website, right to the top on almost all searches when it was previously struggling to make any ground.